I love articles like this. I feel like too often in science education (at least my science education) that laws and theories are presented as just something that you need to memorize, when in my opinion the stories of how things were originally discovered and figured out is eminently more fascinating and inspiring. Like I remember having to learn all of these biochemical pathways, but I left school with nary a clue as to how these pathways were uncovered in the first place.
Thanks for submitting! Would welcome suggestions for any other publications on how scientific theories were first discovered.
Did you get your physics education in high school or university? I only had to take one physics class in the USA at college for my major, quantum electrodynamics for electrical engineering but my professor wrote the textbook and I recall he went over each experiment starting from the fundamentals of our understanding of the basics of the atom, Newton's understanding of light at the time, double slit experiment, to Maxwell's equations, the Michelson Morley ether experiment, to deriving then proving experimentally proving general relativity and decomposing GR into Newtonian physics/other laws of electromagnetism, I am still in awe at the people just figuring this stuff out from first principles.
Anyways, I haven't read this (have it on hold at my library) but someone recommended this book on reddit How to Make an Apple Pie from Scratch: In Search of the Recipe for Our Universe, from the Origins of Atoms to the Big Bang https://www.publishersweekly.com/9780385545655
What’s the name of that textbook? It sounds really interesting.
Isaac Asimov wrote a couple books that follow the narrative of science from the beginnings up until the 80s or so, which I highly recommend. One is called Atom and is more focused on how we got to our “present” understanding of particles. There’s also one that takes a broader view, it’s something like History of Science (? not at my bookshelf right now).
There’s several books in this genre for math as well. IMO it’s a much better structure for pedagogy since we can piggy back the education on our natural wiring to care about narrative and mystery/puzzles.
You're referring to The History of Physics. An excellent read for a budding mind.
Asimov was incredibly talented.
I was looking at my parent's bookshelf and saw a book on Shakespeare and I recognized the author's name: Asimov!
https://en.wikipedia.org/wiki/Asimov's_Guide_to_Shakespeare
It's like 800 pages, I haven't read it but I think I'll keep that one. Seems like it might be hard to find another physical copy. He was definitely prolific on a number of topics.
Not surprising!
"Asimov was so prolific and diverse in his writing that his books span all major categories of the Dewey Decimal Classification except for category 100, philosophy and psychology" - from his Wikipedia page.
His book "Understanding Physics" is amazing. Similar in spirit to Petzold's "Code" that is often praised on HN.
That was my Physics too, but Chemistry just completely glanced over the history. Same thing with Mathematics, no backstory of mathematicians. I guess that either 1. Physics History is short enough, well-recorded, or 2. Physicists really like teaching their history.
Physicists seem to be always seeking a deeper understanding of everything, more so than other fields like biology and sometimes chemistry, who have a tendency to get bogged down into to the idiosyncrasies of particular phenomena.
Yeah, in retrospect I think this aligns with my experience. But I'd even say that with the famous physics experiments I still remember often thinking "How did they get such precision with such primitive instruments?" I mean they would explain the experiments in very basic/schematic terms, but would have been nice to actually replicate I've to truly understand how it worked.
MIT has an excellent chem course on YouTube that goes into the history
> experimentally proving general relativity
Can you elaborate on that? What experiments did the professor perform?
I mis wrote, he talked about the experiments done to verify general and special relativity. Michelson-Morley was one of them that sticks in my mind along with some traveling atomic clocks. We never recreated the experiments like some of the other commenters did in their classes.
The journey behind scientific discoveries for me is as captivating as the discoveries themselves
I read Chasing the Molecule by John Buckingham recently and thoroughly enjoyed it! It give a good outline of the history of modern chemistry in a way that felt accessible but still thorough.
It also does a great job of explaining the different characters and their stories. Some little-known who moved chemistry forwards in profound ways, and others, very well-known, who through their loyalty to false theories ended up holding it back.
It's also a pretty short book when helps make it feel accessible.
Discovering the quantization of the charge of electrons sounds like something you'd be interested in: https://en.wikipedia.org/wiki/Oil_drop_experiment
We did it with several hundred volts (DC, scary) in college and it was pretty fun collecting the data and watching the numbers fall out in excel doing the analysis.
We also did it in uni, it was very exhausting. And after a full day of measurements noone ever had enough data to see the quantization of the charge of electrons.
I remember doing this one and the equipment leaking oil all over me! Not long after that I decided to go more Theoretical…
So very true. The greatest science teachers understand the power that comes with the stories of scientific discovery.
Carl Sagan’s Cosmos and some of Richard Feynman’s best lectures come to mind as some of the most memorable examples, but I’m certain all the best teachers out there know to incorporate the historical and human aspects to bring the essential perspective and natural mnemonic anchors to otherwise “dry” subjects.
As part of 9th grade biology we had to read "Microbe Hunters". The grades ahead insisted that it was awful and boring but I devoured the whole thing in a weekend. So thankful that it was part of the curriculum.
I highly recommend this book! https://www.goodreads.com/book/show/25238350-the-hunt-for-vu...
I'd recommend this one instead: https://en.wikipedia.org/wiki/A_Short_History_of_Nearly_Ever...
How we derived the laws and theories is science. (Some of the other commenters are mixing this together with biographies of the scientists, which is not science but is sometimes interesting in its own right.) The laws and theories in isolation are just trivia, and any class that teaches just those cannot truthfully be called a science class. Demand a better education.
Both have their value, both the process and the results. And given the immensity of scientific knowledge, you can only learn so much of it in a K-12 education, or even in college.
I don't think it's a priori wrong to teach students our current understanding of the world, without going into the details of how we came up with it. I also don't think it's wrong to add those details, but the more details you add, the less of the full picture you'll be able to present. And I definitely don't think it would be a good idea to teach children how we do science, without teaching them what we actually learned from doing it.
I'd also say that the reality of some of the process is extraordinarily boring ("we kept meticulous records of precisely where on the sky various stars were each night, and how their position changed, for a few hundred years, and tried finding a function that matched those numbers; for a few hundred years, we kept adding more and more circles to correct things, until Kepler came up with some ellipses"). And that for many children, learning history is already a huge bore, learning the history of science in addition would make science classes much worse. For others, the opposite is true.
When I was a tutor, mostly doing math, when it came to polynomials and that range, I would trick my students into deriving the quadratic equation. It's not even a full page. Almost all of them finished with a strange expression, and then we had the little "it was always there, waiting for someone to find it" chat.
Some people care about the history, some don't. I find when people talk about astrophysics stuff, most of them do not know the history and ought to, because most of their interpretations fall into the "Yes, that was a question in the 1960s but eventually ..."
If you want one for relativity, I strongly suggest Was Einstein Right? by Clifford Will. It dates from 1986, so it is nearly forty years behind now, but it covers the many experiments and tests of relativities special and general.
In 1676 Roemer estimated the speed of light by timing the orbit of Jupiter’s moon Io, noting that as the Earth approached Jupiter, Io emerged from behind Jupiter a little earlier every day, and as the Earth traveled away from Jupiter it appeared a little later every day, with the time of day varying by 22 minutes over a year. Knowing the difference between the two distances, he reckoned that light travels that distance in 22 minutes, or 227 thousand km/s. The actual speed is about 300 thousand km/s. Not bad!
I always appreciate these stories about how very specific observations that most people would miss can give away far deeper details of the universe that many wouldn't even consider. Eratosthenes using shadows and figuring out the size of the earth within a few percent is another well known one.
It's amazing to think that with nothing more than a telescope and careful timing, he managed to get so close to the actual speed of light.
The title of this thread appears to be wrong, because the parent article says
"But a little experiment that Rayleigh performed in 1890, inspired directly by Franklin's observations, is not nearly as well-known."
Therefore Rayleigh computed the size of molecules in 1890, not in 1870 (in 1870 Rayleigh was young and not known yet for any original research).
While Rayleigh has devised a novel method for determining the size of molecules, it should be noted that the first who has succeeded to determine the size and weight of molecules was Johann Josef Loschmidt, in 1865.
https://en.wikipedia.org/wiki/Johann_Josef_Loschmidt
The publication of the weight and size of air molecules by Loschmidt is one of the most important milestones in the history of physics.
Until that moment in 1865, the theory of atoms revived by Dalton could still be considered as some kind of fictitious model that explained some features of the chemical reactions and of thermodynamics, but which might have been wrong and which would probably be replaced by some better model.
Starting from that moment, the atoms and molecules could be weighed and counted, so their reality was no longer questioned.
The determination by Loschmidt of the size and weight of air molecules was enough to determine the sizes and weights of any other known atoms and molecules, making use of the relative atomic weights that could be determined from chemical reactions and which were already known.
Moreover, a few years later, in 1874, George Johnstone Stoney has used the results of Loschmidt together with the theory of the existence of an elementary electric charge published by Maxwell one year before, in 1873, to compute the value of the elementary electric charge. Some years later, Stoney has given the name "electron" to the elementary electric charge, which has been the source of a very large number of words in modern science and technology, from electronics to hadrons.
That reminds me of the Millikan & Fletcher oil-drop experiment [0], which measured the charge of the electron.
In short, microscopic atomized oil droplets had their fall-time through air measured to figure out their volume, and then a known electric field was used to levitate them. The calculated charge-per-molecule clustered around multiples of a smaller value, which would be the charge of an individual electron.
They tried a similar experiment first, called the water drop experiment. It was intended to work in the exact same way, except with the obvious parameter varied: they would use water instead of oil.
The reason the water drop experiment failed was that the bright lamps they used to look at the drops evaporated the water too quickly.[1] Such a relatable experience!
[1]: https://buttondown.com/entropicthoughts/archive/when-bubble-...
There is always more to the story:
https://www.scribd.com/document/661270387/My-Work-with-Milli... Fletcher & Millikan
How can you make sure you don't end up with 2e as a result? (Or any other multiple)
For that to happen, you would have to be very unlucky: all of your measurements would have to be 2e, 4e, 6e, etc. If a 3e or 5e sneaked in there, you'd realize that the charge was e, not 2e. With enough measurements, you can be confident that you've hit all the expected multiples of the quantum.
Not quite so. They did end up measuring a multiple of the fundamental electric charge. The experiment really measured 3e, 6e, 9e, etc. It turns out that the electron and proton have an electric charge 3× bigger than that of a quark. Since the experiment didn’t generate any free quarks, nobody noticed for years. Even today the mistake persists and school children are taught, unironically, that down quarks have ±⅓ of the fundamental indivisible unit of electric charge and that up quarks have ±⅔e.
In 1909 the results results were couched in some "elementary electric charge" quantity, since the now-familiar subatomic particle model (and the "electron") was still gaining acceptance.
I expect that the greater the number of trials, it becomes easier it is to detect a distinction between closer-multiples, and if at some point more trials stops changing the answer then you've likely converged on e, unless there's some new principle like "X-ray exposure only affects charge in in multiples of e greater than one."
The approximate value of the elementary electric charge had been known since 1874, when it was first computed by George Johnstone Stoney. After Stoney, other experiments had reduced the uncertainty with which the value was known, but it remained relatively high.
The importance of the experiments of Robert Andrews Millikan consists in the fact that the uncertainty of the value of the elementary electric charge obtained by this method was much smaller than by any previous method (he claimed that it was better than one half of one percent, but he used wrong values for the viscosity of air, so his actual result was off by more than that, but still by less than one percent from the correct result).
You do. Thae size of the steps between the results is the “quantum” of a single transferable charge.
He did- he selected the lowest value, ignoring all the multiples.
Not ignoring the multiples; the multiples verify the result.
If you calculate the charge of one at 1e and you measure 2.5e, something went wrong. All values must be a multiple of the lowest.
This is fascinating, but wasn't it still a bit of a conjecture to assume the oil would spread to a minimum thickness of one molecule? Did he have any doubts, like that surface tension might keep it thicker? Or other clues hinting it was indeed a monolayer?
My question exactly.. I hope someone can chime in :)
EDIT: Thinking a bit more... I suppose it's a reasonable assumption that the molecules (mostly) wouldn't stack on top of each other. They all want to get lower and perhaps the resistance to the oil spreading out is much lower proportionately that the gravitational force encouraging the oil to flatten
But if I spill some oil on my plate it doesn't look a molecule thin to me. Why is it different with water?
I guess oil is repelled by water, so when it's poured on top of water it's more like floating on top. So the water pushes up, gravity pulls down and the oil molecules pull on each-other, there is no horizontal friction, allowing the oil to spread out this way. Whereas the oil does slightly stick to your plate, as can be observed when moving the plate around, so it won't spread as thinly?
"Rayleigh divided the volume of the oil by the area it covered, thus estimating the thickness of the oil film. Assuming that the oil formed a single layer of molecules — a monolayer — then the thickness of the oil film is the same thing as the length of one oil molecule.
This is how Lord Rayleigh became the first person to figure out a single molecule’s dimensions, many years before anyone could see such molecules."
> Assuming that the oil formed a single layer of molecules — a monolayer — then the thickness of the oil film is the same thing as the length of one oil molecule.
How did he know that the film of oil was one molecule thick?
It feels like a huge assumption to me, but maybe this blog post left something out.
Blog post seems to have elided this point, but it did link the original paper which was quite short: https://www.damtp.cam.ac.uk/user/gold/pdfs/teaching/old_lite...
Rayleigh's experiment was actually trying to solve for the minimum thickness of oil required to stop some camphor shavings from moving around on the water. He never states it explicitly, but I think the assumption is that the minimum thickness required to stop the shavings' movement would be such that the oil volume 'just' covers the surface, ie. is 1 molecule thick everywhere and hence the shavings never touch water. I think he's specifically making a slightly more clever point about surface tension, but that's a little beyond me.
Camphor would release compounds that adjust the surface tension of water. So the oil would break that direct relationship.
If you try the experiment lots of times with drops of different sizes you find the oil layer always has roughly the same thickness. That's an interesting observation that calls for some kind of explanation, and the hypothesisis that the thickness of the oil layer is the length of one molecule is perhaps the most obvious and plausible explanation. Then one would look for confirmation, of course. (What was the next thing to confirm this, historically?)
It feels intuitive that a thin fluid on a low-friction surface (like water) would spread out "as much as possible" given enough time. There certainly may be confounding factors, but it seems like a reasonable thing to pin as an "assumption" in a hypothesis. I.e. he didn't have to "know" - assumptions are OK, and I don't feel like this one is huge.
> It feels intuitive that a thin fluid on a low-friction surface (like water) would spread out "as much as possible" given enough time.
Most fluids do not behave this way in most circumstances, because of surface tension, so it's really not intuitive.
This experiments is one of the few ways you can get an accurate measurement. Many other fluids will either mix or end up as bubbles/blobs many orders of magnitude thicker than a molecule.
I'm confused, the blog wrote "known amount of water," so was it a closed little area like a bathtub? If you added a ton of oil wouldn't it spread out as much as possible aka 600 molecules thick or whatever?
Or did he pour it into a huge lake or something?
One drop in a soup bowl sized petri dish, measure the area it covers.
Surely the first thing to test would be dropping it in increasingly large soup bowls until there's obvious gaps?
How would the gaps be obvious? I'm not sure I could tell 1 molecule from 0 molecules when it comes to the thickness of oil film.
Agreed. The experiment actually gives an upper limit on the size of a molecule in one particular dimension. Still a very useful result.
It isn’t necessarily an upper bound. The molecules might spread out more distant than their size.
In a very unlucky world, they can form a 2D net, with molecules instead of strings and a lot of tiny holes.
If this seams impossible, remember that when water freeze into ice, it expands to a 3D "net" with empty holes.
Wouldn't that provide an upper bound then? If the real size is equal to or less than the calculated size?
Scientists frequently have to make assumptions in order to make progress.
Famous example is Darwin figured out that traits are inheritable by natural selection, and this is the driving force of evolution, without having any concept of the physical nature of DNA, or how genes could change (eg. by DNA mutation) to develop adaptations and thus make an organism more fit.
If there were multiple layers of molecules then the film would spread out over a wider area. With repeated experiments it would be clear that films are always an integer multiple of this thickness and never thinner.
I have also immediately thought the same question. This is probably the most crucial part of the whole estimation and indeed left out in the article.
Perhaps at the time it was sufficient to define "molecule of oil" as "the height of the amount when spread maximally across the surface of water", and it just so happens that height is only 1 actual molecule
> How did he know that the film of oil was one molecule thick?
He didn't. It was an assumption
Cool article. They somehow got the formula wrong though, the formula on the screenshot has an additional factor of 0.9 that accounts for the fact that 1l of oil is not 1 kg. Perhaps it's intentional, but for something so simple I don't think it needs to be dumbed down even further.
I would have loved to have had a course in school about "The Design of Scientific Experiments." One that described the processes of landmark historical experiments from antiquity onward, and challenged students throughout: "Given this set of constraints, how would you design and execute an experiment to estimate the size of the Earth? Disprove phlogiston and luminiferous aether? Measure the speed of light?"
I don't think many people today would be able to propose the Michelson Morley experiment and then actually do it. It was truly heoric (and Michelson was a genius).
We did this oil/water experiment in freshman physics or chemistry lab. It was rushed, everybody just did the minimum, the teachers barely explained any of it, and then we moved on.
I agree. The Michelson Morley experiment reminds me of some difficult algorithms: simple only in hindsight, and implementation is _hard_ to do correctly.
People still win Nobel prizes (LIGO, for example) using interferometers. It’s arguably the single greatest invention in experimental physics.
That would have been an incredible course!
Experiments are HARD. There is a joke among physicists that theoreticians are washed up by 35 but experimentalists don't even get started until 45.
To make a physics experiment work you have to be ridiculous about recording details and have a strong intuition. You have to design the experiment such that you can differentiate between "hypothesis wrong" and "equipment doesn't work" because you don't know the answer.
(For example: When they turned on LIGO for the first time, they almost immediately caught a great event. Huge victory party, right? Nope. They promptly ignored it assuming that something was wrong with the machine. And it was only after significant post analysis and correlation that they decided that it was a real event.)
The lengths they're going to fix the "loopholes" in the Bell Inequality tests are amazing.
100% true
And this is my sticking point with a lot of "Science skeptics" around that have skepticism as their personality
Make no mistake, I do take scientific discoveries and knowledge very serious, and knowing the stories make it appreciate more the efforts and the work it took to get there
But a lot of times people think the experiments give a very clear-cut results, when it's more like "one line is squiggly down and the other is squiggly up" with data being barely over 5 sigma
https://www.atomsonly.news/p/franklin-oil
Why this domain has been suspended
Since January 2014, all ICANN accredited registrars (like Namecheap) have been required to verify the contact information (Registrant Whois) of customers registering domain names. This includes modifications to the contact details.
Thanks for covering that story - I lived at Clapham Common for seven happy years.
So much history: there is also a little church on the Common, whose past members played a role in the abolishion of slavery: https://en.wikipedia.org/wiki/Clapham_Sect
> and he charted the Gulf Stream’s course across the Atlantic ocean, noting that ships traveling from America to England took longer than those going the opposite direction
?? Has the Gulfstream changed direction in the intervening years?
We recreated this experiment in one of my university physics classes. It was a lot of work, and our results weren't nearly as good, but it was instructive and interesting. The equipment requirements were completely reasonable for an undergrad physics lab. I highly recommend giving it a try if you can.
Very cool.
For more like this, check out this lecture series: https://www.thegreatcoursesplus.com/the-evidence-for-modern-...
It's by a guy called Don Lincoln and it's about how we established things like the existence of atoms, the speed of light, and many other fundamental things that are good to know.
It's also an audiobook, though the lectures are easier to follow.
A few days ago, there was a HN post about surface acoustic wave filters, and a commenter mentions how inspired the inventor of it must have been(https://news.ycombinator.com/item?id=41604937).
That was this same fella!
Fun fact: Every 4 days humanity produces enough oil to cover the entirety of the world's oceans.
Source: Public statistics and my back-of-napkin math, not accounting for waves.
I went to a talk by a very old physicist. At the end of his talk, he said, recalling from memory, all of the great experiments of the past were done by nothing. If an experiment costs more than $100, I am out.
His setup has mud in a jar and bacteria in it which you can see with a simple microscope or handheld lens.
That's a bit harsh. To give one counterexample, the Michelson-morley experiment put the figurative nail in the coffin of centuries of speculation about the "luminiferous aether". The experimental apparatus was a table-sized precision carved slab of sandstone floating in a huge vat of mercury, holding the highest precision optical equipment of the day. I suspect it cost rather more than $100 even in the 1880s.
https://archive.is/oMgPW (The domain of the original article seems to be dead)
Even back in the day, without all our modern technology, great minds like Franklin and Rayleigh could uncover truths that still resonate today.
Related: Agnes Pockels’ experiments [0]
Luckily it wasn't my grade that got this experiment as the practical exam in one of the National Physics Olympiads I went to... :) poor souls, most got answers orders of magnitude away.
Site has gone down with a dns error of some kind; anyone have a snapshot?
These are the best kind of posts, where there's something I've never even heard of before. I never knew 'oiling the seas' was a thing, or that it (apparently?) works.
> I love this story because it shows, at least anecdotally, how deep scientific insights can emerge from the simplest of experiments. It's a testament to the idea that you don't always need sophisticated equipment to unlock the secrets of nature — sometimes, all it takes is a drop of oil and a bit of ingenuity.
This can apply to many other fields too!
The credit for proving the existence of atoms is more often associated with Einstein's explanation of Brownian motion and Jean Perrin's experimental confirmation, even though earlier work by Lord Rayleigh, Benjamin Franklin, and others hinted at the molecular structure of matter.
The page is timing out for me, but is it the inverse problem of the time when Steve Mould/Matt Parker measured the unknown quantity π, but already assuming a size of the molecules? Presumably Lord Rayleigh already had a at least a good order-of-magnitude approximation of pi...
By 1870 pi was known to several hundred decimal digits, for something like this calculation where you have other large sources of error Archimedes approximation from 2 millennia earlier would probably be fine. (<1% error)
https://en.m.wikipedia.org/wiki/Chronology_of_computation_of...
Note that pi to 40 digits is sufficient to calculate the circumference of the observable universe to subatomic precision.
I won’t trust this until I myself can calm an acre of water with a teaspoon of oil. (Or at least see a YouTube video of someone doing it)
YouTube video: https://www.youtube.com/watch?v=RST_ylwVrUw&t=1m27s
That's funny, thanks for sharing. I was watching his video where he's saying "you can see it right there, look how much calmer it is, it looks like ice" and was thinking "I don't know what he's talking about I don't see ... oh, that ice patch is water"
Another version is in Phil Morrison's "The Ring of Truth" episode "Atoms" at https://youtu.be/WQ3mjb9BSaU?t=1765 or 29:26 at https://archive.org/details/TheRingofTruth/Ring.of.Truth.S01... .
(It would be nice if archive.org had a way to link to a specific timestamp.)
We did this same experiment in school, with a tiny pinprick of oil, estimating the volume of the drop as a sphere, and a small water tank, and then estimated the area of oil slick as a circle.
Yes, we did it in physics at school too, when we were 13 or 14 I think.
Semi off topic:
Interesting to look at picture of the text of the 1890 paper. That typesetting is almost the same as modern scientific papers.
Maybe Rayleigh had an early copy of LaTeX? ;-)
Thank Knuth for TeX or good scientific typesetting would be a nice thing the Victorians had.
How is the measurement for the area the oil has spread over performed? Visually or some other way?
The actual manuscript from Rayleigh [1] explains it better: the area is the entire area of the vessel the oil was placed in, and the thing actually being measured was how much oil was required for it cover the whole area.
[1] https://www.damtp.cam.ac.uk/user/gold/pdfs/teaching/old_lite...
He used a fixed area (a 33 inch diameter bowl) and measured the weight of oil required to just about calm the entire water. That turned out to be 0.81 milligrams.
Some powder is added to the water, which covers the surface of the water but not the oil patch (which is circular). Then the oil patch diameter is measured.
This was how we did this when we replicated this experiment in high school. I guess from the other responses here that this wasn't common?
When we did it in high school (70's) we just used compound that had a long chain (soap?) and only one end dissolved in the water. It was very easy to measure and calculate the size of the molecule . We had a series of these simple experiments. Another I recall was measure the speed at which certain volatile compounds moved through the air.
I definitely learned that all science doesn't have to involve complex equipment.
The original way was to cover the surface of a round bowl with oil. It certainly makes a lot more sense to me than trying to measure a floating disk of oil.
>"not more than a Tea Spoonful," according to his diary — Franklin poured it onto the agitated water. The oil spread rapidly across the surface, covering "perhaps half an Acre" of the pond and rendering its waters "as smooth as a Looking Glass."
What??
Here's a video from another post: https://news.ycombinator.com/item?id=41630637